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  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
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  • C09K2019/0466—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the linking chain being a -CF2O- chain
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  • C09K19/12—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings at least two benzene rings directly linked, e.g. biphenyls
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  • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
  • C09K19/3001—Cyclohexane rings
  • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
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  • C09K2323/03—Viewing layer characterised by chemical composition

Definitions

• the present invention relates to liquid-crystalline media (LC media) comprising thiophene derivatives and to liquid-crystal displays (LC displays) containing these LC media.
• the media have high optical anisotropy and preferably have a content of thiophene derivatives of 25% by weight or more.
• Liquid crystals are used principally as dielectrics in display devices, since the optical properties of such substances can be modified by an applied voltage.
• Electro-optical devices based on liquid crystals are extremely well known to the person skilled in the art and can be based on various effects. Examples of such devices are cells having dynamic scattering, DAP (deformation of aligned phases) cells, guest/host cells, TN cells having a twisted nematic structure, STN (supertwisted nematic) cells, SBE (superbirefringence effect) cells and OMI (optical mode interference) cells.
• DAP deformation of aligned phases
• guest/host cells guest/host cells
• TN cells having a twisted nematic structure
• STN (supertwisted nematic) cells SBE (superbirefringence effect) cells
• OMI optical mode interference
• the commonest display devices are based on the Schadt-Helfrich effect and have a twisted nematic structure.
• TN, STN and IPS cells are currently commercially interesting areas of application for the media according to the invention.
• the liquid-crystal materials must have good chemical and thermal stability and good stability to electric fields and electromagnetic radiation. Furthermore, the liquid-crystal materials should have low viscosity and produce short addressing times, low threshold voltages and high contrast in the cells.
• a suitable mesophase for example a nematic mesophase for the above-mentioned cells, at the usual operating temperatures, i.e. in the broadest possible range above and below room temperature.
• a suitable mesophase for example a nematic mesophase for the above-mentioned cells
• liquid crystals are generally used as mixtures of a plurality of components, it is important that the components are readily miscible with one another.
• the individual compounds should have high solubility in a typical mixture, also called the host.
• Further properties, such as the electrical conductivity, the dielectric anisotropy and the optical anisotropy have to satisfy various requirements depending on the cell type and area of application. For example, materials for cells having a twisted nematic structure should have positive dielectric anisotropy and low electrical conductivity.
• Matrix liquid-crystal displays of this type are known. Examples of non-linear elements which can be used to individually switch the individual pixels are active elements (i.e. transistors).
• active matrix is then used, where a distinction can be made between two types:
• the electro-optical effect used is usually the TN effect.
• TFTs comprising compound semiconductors, such as, for example, CdSe, or TFTs based on polycrystalline or amorphous silicon. Intensive work is being carried out worldwide on the latter technology.
• the TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counterelectrode on its inside. Compared with the size of the pixel electrode, the TFT is very small and has virtually no adverse effect on the image.
• This technology can also be extended to fully colour-capable displays, in which a mosaic of red, green and blue filters is arranged in such a way that a filter element is opposite each switchable pixel.
• the TFT displays usually operate as TN cells with crossed polarisers in transmission and are backlit.
• MLC displays of this type are particularly suitable for TV applications (for example pocket televisions) or for high-information displays for computer applications (laptops) and in automobile or aircraft construction.
• TV applications for example pocket televisions
• high-information displays for computer applications (laptops) and in automobile or aircraft construction.
• difficulties also arise in MLC displays due to insufficiently high specific resistance of the liquid-crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, pp.
• the specific resistance exhibits the smallest possible increase with increasing temperature and after heating and/or UV exposure.
• the low-temperature properties of the mixtures from the prior art are also particularly disadvantageous. It is demanded that no crystallisation and/or smectic phases occur, even at low temperatures, and the temperature dependence of the viscosity is as low as possible.
• the MLC displays from the prior art thus do not satisfy today's requirements.
• MLC displays having short response times are required. Such short response times can be achieved, in particular, if liquid-crystal media having low values for the viscosity, in particular the rotational viscosity ⁇ 1 , are used.
• diluting additives generally lower the clearing point and thus reduce the working-temperature range of the medium.
• electro-optical devices which operate with LC media. These include printers, scanners, lenses, exposure apparatuses and electro-optical shutters. The latter can be used in technical apparatuses or cameras, and recently also in displays for three-dimensional (3D) images.
• 3D display devices use fast-switching LC media as shutter in order to generate separate beams alternately for addressing the left and right eye of a viewer.
• the LC medium here can be accommodated, depending on the 3D technology, in spectacles or in a part of the screen. Very fast response times are necessary for such applications.
• High birefringence is likewise desirable in many cases in order, for example, to achieve controllable light diffraction for LC lenses.
• These switchable lenses can be employed in autostereoscopic displays consisting of a switchable 2D display and switchable optical elements which are able to change between a 2D mode and a 3D mode.
• the lenses designed as switchable lenticular lenses, fan out the pixel contents of the 2D display into the room.
• Each fan element contains the information of a 3D content from a certain viewing angle. If the two eyes of a viewer are located in adjacent fans, the viewer perceives a spatial stereoscopic image.
• the switchable lens here can be implemented as a liquid-crystal GRIN lens (‘gradient index lens’) or as a liquid-crystal replica lens.
• gradient index lens liquid-crystal GRIN lens
• LC medium high optical birefringence of the LC medium used is desirable.
• the invention is based on the object of providing media, in particular for MLC, TN, STN or IPS displays of this type, which have the desired properties indicated above and do not exhibit the disadvantages indicated above or only do so to a lesser extent.
• the LC media should have fast response times and low rotational viscosities at the same time as high dielectric anisotropy and high birefringence.
• the LC media should have a high clearing point, a broad nematic phase range and a low threshold voltage.
• thiophene compounds have been described as liquid crystals. Compounds and mixtures are known, for example from the specification WO 2009/129915 A1. The proportion of thiophene compounds therein is 3 to 18% by weight.
• the present invention thus relates to an LC medium comprising one or more compounds of the formula I
• the invention preferably relates to an LC medium which has at room temperature a nematic phase, preferably achiral, comprising one or more compounds of the formula I.
• the media have high optical anisotropy and preferably have a content of thiophene derivatives of 25% by weight or more.
• the invention furthermore relates to the use of LC media according to the invention in electro-optical displays, in particular LC displays.
• the invention furthermore relates to an LC display or an electro-optical device containing one or more compounds of the formula I (preferably 25% by weight or more) or an LC medium according to the invention.
• an LC display or an electro-optical device containing one or more compounds of the formula I (preferably 25% by weight or more) or an LC medium according to the invention.
• it is an MLC, TN, STN or IPS display or an electro-optical switchable lens or a shutter, preferably for an LC display, camera, printer or exposure apparatus.
• the medium preferably comprises 25-80% by weight, preferably 30% by weight or more, and particularly preferably 40% by weight or more, of compounds of the formula I.
• the rings A 1 in formula I particularly preferably denote phenylene-1,4-diyl, which may also be mono- or polysubstituted by F.
• a 1 in formula I particularly preferably denotes a radical of the formula
• L denotes halogen, preferably F.
• R 1 and R 2 each, independently of one another, denote unbranched alkyl, alkenyl or alkynyl having 1 to 8, preferably 1 to 5, C atoms, each of which is optionally substituted by halogen, in particular by F.
• R 1 is very particularly preferably equal to alkyl.
• R 1 is alkyl and R 2 is H or alkyl.
• R 1 , R 2 each, independently of one another, very particularly preferably denote unbranched alkyl having 1-5 C atoms. If R 1 and R 2 denote substituted alkyl, alkoxy, alkenyl or alkynyl, the total number of C atoms in the two groups R 1 and R 2 is preferably less than 10.
• Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl and n-octyl.
• Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl and pentenyl.
• Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl and octynyl.
• Preferred alkoxy groups are, for example, methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy.
• Halogen preferably denotes F or Cl.
• Particularly preferred compounds of the formula I are those selected from the following sub-formulae:
• R 1 and R 2 have the meanings indicated above and below.
• R 1 and R 2 therein preferably denote optionally fluorinated alkyl, alkenyl, alkynyl or alkoxy having 1 to 12 C atoms, particularly preferably optionally fluorinated alkyl, alkenyl or alkynyl having 1 to 6 C atoms.
• the compounds of the formulae I1 to I37 are particularly preferred owing to the high dielectric anisotropy in relation to the viscosity, in particular compounds I1 to I27, and very particularly compounds of the formula I6.
• thiophenes of the formula I are known, for example from WO 2009/129915 A1 and the international applications PCT/EP2010/000636 and PCT/EP2010/000968.
• Further compounds of the formula I can be prepared analogously to processes which are known and/or described in standard works of organic chemistry, such as, for example, in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme-Verlag, Stuttgart, and analogously to the example syntheses.
• the compounds of the formula II are preferably selected from the group consisting of the following formulae:
• the compounds of the formula III are preferably selected from the group consisting of the following formulae:
• X 0 preferably denotes F or OCF 3 , furthermore OCHF 2 , CF 3 , CF 2 H, Cl, OCH ⁇ CF 2 .
• R 0 is preferably straight-chain alkyl or alkenyl, each having up to 6 C atoms.
• the compounds of the formula IV are preferably selected from the group consisting of the following formulae:
• R 0 in formula IV denotes alkyl having 1 to 8 C atoms and X 0 denotes F, Cl, OCHF 2 or OCF 3 , furthermore OCH ⁇ CF 2 .
• R 0 preferably denotes alkyl or alkenyl.
• X 0 preferably denotes Cl, furthermore F.
• the compounds of the formula V are preferably selected from the group consisting of the following formulae:
• R 0 in formula VI denotes alkyl having 1 to 8 C atoms and X 0 denotes F;
• the compounds of the formula VIII are preferably selected from the group consisting of the following formulae:
• the compounds of the formula IX are preferably selected from the group consisting of the following formulae:
• the compounds of the formulae X and XI are preferably selected from the group consisting of the following formulae:
• Preferred compounds of the formula XII are those selected from the group consisting of the following formulae:
• the compounds of the formulae XIII and XIV are preferably selected from the group consisting of the following formulae:
• alkyl or “alkyl*” in this application encompasses straight-chain and branched alkyl groups having 1-7 carbon atoms, in particular the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups having 1-6 carbon atoms are generally preferred.
• alkenyl or “alkenyl*” in this application encompasses straight-chain and branched alkenyl groups having 2-7 carbon atoms, in particular the straight-chain groups.
• Preferred alkenyl groups are C 2 -C 7 -1E-alkenyl, C 4 -C 7 -3E-alkenyl, C 5 -C 7 -4-alkenyl, C 6 -C 7 -5-alkenyl and C 7 -6-alkenyl, in particular C 2 -C 7 -1E-alkenyl, C 4 -C 7 -3E-alkenyl and C 5 -C 7 -4-alkenyl.
• alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5 carbon atoms are generally preferred.
• fluoroalkyl in this application encompasses straight-chain groups containing at least one fluorine atom, preferably a terminal fluorine, i.e. fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl and 7-fluoroheptyl. However, other positions of the fluorine are not excluded.
• halogenated alkyl radical preferably encompasses mono- or polyfluorinated and/or -chlorinated radicals. Perhalogenated radicals are included. Particular preference is given to fluorinated alkyl radicals, in particular CF 3 , CH 2 CF 3 , CH 2 CHF 2 , CHF 2 , CH 2 F, CHFCF 3 and CF 2 CHFCF 3 .
• R 0 in the formulae above and below denotes an alkyl radical and/or an alkoxy radical, this may be straight-chain or branched. It is preferably straight-chain, has 2, 3, 4, 5, 6 or 7 C atoms and accordingly preferably denotes ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexyloxy or heptyloxy, furthermore methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.
• R 0 denotes an alkyl radical in which a CH 2 group has been replaced by —CH ⁇ CH—, this may be straight-chain or branched. It is preferably straight-chain and has 2 to 10 C atoms. Accordingly, it denotes, in particular, vinyl, prop-1- or -2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl, dec-1-, -2-, -3-, -4
• R 0 denotes an alkyl or alkenyl radical which is at least monosubstituted by halogen
• this radical is preferably straight-chain, and halogen is preferably F or Cl.
• halogen is preferably F.
• the resultant radicals also include perfluorinated radicals.
• the fluorine or chlorine substituent may be in any desired position, but is preferably in the ⁇ -position.
• X 0 is preferably F, Cl or a mono- or polyfluorinated alkyl or alkoxy radical having 1, 2 or 3 C atoms or a mono- or polyfluorinated alkenyl radical having 2 or 3 C atoms.
• X 0 is particularly preferably F, Cl, CF 3 , CHF 2 , OCF 3 , OCHF 2 , OCFHCF 3 , OCFHCHF 2 , OCFHCH 2 F, OCF 2 CH 3 , OCF 2 CHF 2 , OCF 2 CH 2 F, OCF 2 CF 2 CHF 2 , OCF 2 CF 2 CH 2 F, OCFHCF 2 CF 3 , OCFHCF 2 CHF 2 , OCH ⁇ CF 2 , OCF ⁇ CF 2 , OCF 2 CHFCF 3 , OCF 2 CF 2 CF 3 , OCF 2 CF 2 CClF 2 , OCClFCF 2 CF 3 , CF ⁇ CF 2 , CF ⁇ CHF, or CH ⁇ CF 2 , very particularly preferably F, OCF 3 or OCH ⁇ CF 2 .
• R 0 and X 0 Through a suitable choice of the meanings of R 0 and X 0 , the addressing times, the threshold voltage, the steepness of the transmission characteristic lines, etc., can be modified in the desired manner.
• 1E-alkenyl radicals, 3E-alkenyl radicals, 2E-alkenyloxy radicals and the like generally result in shorter addressing times, improved nematic tendencies and a higher ratio between the elastic constants k 33 (bend) and k 11 (splay) compared with alkyl and alkoxy radicals.
• 4-Alkenyl radicals, 3-alkenyl radicals and the like generally give lower threshold voltages and lower values of k 33 /k 11 compared with alkyl and alkoxy radicals.
• the mixtures according to the invention are distinguished, in particular, by high K 1 values and thus have significantly faster response times than the mixtures from the prior art.
• the optimum mixing ratio of the compounds of the above-mentioned formulae depends substantially on the desired properties, on the choice of the components of the above-mentioned formulae and on the choice of any further components that may be present.
• the total amount of compounds of the above-mentioned formulae in the mixtures according to the invention is not crucial.
• the mixtures can therefore comprise one or more further components for the purposes of optimisation of various properties.
• the observed effect on the desired improvement in the properties of the mixture is generally greater, the higher the total concentration of compounds of the above-mentioned formulae.
• the media according to the invention comprise compounds of the formulae IV to VIII in which X 0 denotes F, OCF 3 , OCHF 2 , OCH ⁇ CF 2 , OCF ⁇ CF 2 or OCF 2 —CF 2 H.
• X 0 denotes F, OCF 3 , OCHF 2 , OCH ⁇ CF 2 , OCF ⁇ CF 2 or OCF 2 —CF 2 H.
• the invention also relates to electro-optical displays, such as, for example, TN, STN, TFT, OCB, IPS, FFS or MLC displays, having two planeparallel outer plates, which, together with a frame, form a cell, integrated non-linear elements for switching individual pixels on the outer plates, and a nematic liquid-crystal mixture having positive dielectric anisotropy and high specific resistance located in the cell, which contain media of this type, and to the use of these media for electro-optical purposes.
• electro-optical displays such as, for example, TN, STN, TFT, OCB, IPS, FFS or MLC displays, having two planeparallel outer plates, which, together with a frame, form a cell, integrated non-linear elements for switching individual pixels on the outer plates, and a nematic liquid-crystal mixture having positive dielectric anisotropy and high specific resistance located in the cell, which contain media of this type, and to the use of these media for electro-optical purposes
• liquid-crystal mixtures according to the invention enable a significant broadening of the available parameter latitude.
• achievable combinations of clearing point, viscosity at low temperature, thermal and UV stability and high optical anisotropy are far superior to previous materials from the prior art.
• the mixtures according to the invention are particularly suitable for mobile applications and high- ⁇ n TFT applications, such as, for example, PDAs, notebooks, LCD TVs and monitors.
• liquid-crystal mixtures according to the invention with retention of the nematic phase down to ⁇ 20° C. and preferably down to ⁇ 30° C., particularly preferably down to ⁇ 40° C., and of the clearing point ⁇ 70° C., preferably ⁇ 75° C., simultaneously enable rotational viscosities ⁇ 1 of 100 mPa ⁇ s, particularly preferably ⁇ 70 mPa ⁇ s, to be achieved, enabling excellent MLC displays having fast response times to be obtained.
• the dielectric anisotropy ⁇ of the liquid-crystal mixtures according to the invention is preferably ⁇ +3, particularly preferably ⁇ +5.
• the mixtures are characterised by low operating voltages.
• the threshold voltage of the liquid-crystal mixtures according to the invention is preferably ⁇ 2 V, in particular ⁇ 1.5 V.
• the birefringence ⁇ n of the liquid-crystal mixtures according to the invention is preferably ⁇ 0.11, particularly preferably ⁇ 0.14.
• the nematic phase range of the liquid-crystal mixtures according to the invention preferably has a width of at least 80°, in particular at least 90°. This range preferably extends at least from ⁇ 20° C. to +70° C.
• the MLC displays according to the invention preferably operate at the first Gooch and Tarry transmission minimum [C. H. Gooch and H. A. Tarry, Electron. Lett. 10, 2-4, 1974; C. H. Gooch and H. A. Tarry, Appl. Phys., Vol.
• the LC media are preferably 99% by weight, particularly preferably 100% by weight, free from benzonitrile derivatives.
• the light stability and UV stability of the mixtures according to the invention are considerably better, i.e. they exhibit a significantly smaller decrease in the HR on exposure to light or UV. Even low concentrations of the compounds ( ⁇ 10% by weight) of the formula I in the mixtures increase the HR by 6% or more compared with mixtures from the prior art.
• the LC media may also comprise further additives known to the person skilled in the art and described in the literature, such as, for example, UV stabilisers, such as Tinuvin® from Ciba, antioxidants, free-radical scavengers, nanoparticles, etc.
• UV stabilisers such as Tinuvin® from Ciba
• antioxidants such as antioxidants, free-radical scavengers, nanoparticles, etc.
• 0-15% of pleochroic dyes or chiral dopants can be added.
• Suitable stabilisers and dopants are mentioned below in Tables C and D.
• the LC media according to the invention may also comprise compounds in which, for example, H, N, O, Cl, F have been replaced by the corresponding isotopes.
• liquid-crystal mixtures which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing one or more compounds of the formula I with one or more compounds of the formulae II-XXVIII or with further liquid-crystalline compounds and/or additives.
• the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature.
• solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing.
• the invention furthermore relates to the process for the preparation of the LC media according to the invention.
• the construction of the MLC display according to the invention from polarisers, electrode base plates and surface-treated electrodes corresponds to the usual design for displays of this type.
• the term usual design is broadly drawn here and also encompasses all derivatives and modifications of the MLC display, in particular including matrix display elements based on poly-Si TFTs or MIM.
• the LC media according to the invention comprise one or more compounds selected from the group consisting of compounds from Tables A and B.
• Table C indicates possible dopants which can be added to the LC media according to the invention.
• the LC media preferably comprise 0 to 10% by weight, in particular 0.01 to 5% by weight and particularly preferably 0.1 to 3% by weight, of dopants.
• the LC media preferably comprise one or more dopants selected from the group consisting of compounds from Table C.
• the LC media preferably comprise 0 to 10% by weight, in particular 0.01 to 5% by weight and particularly preferably 0.1 to 3% by weight, of stabilisers.
• the LC media preferably comprise one or more stabilisers selected from the group consisting of compounds from Table D.
• temperature values indicated in the present application such as, for example, the melting point T(C,N), the transition from the smectic (S) to the nematic (N) phase T(S,N) and the clearing point T(N,I), are indicated in degrees Celsius (° C.).
• M.p. denotes melting point
• cl.p. clearing point.
• C crystalline state
• N nematic phase
• S smectic phase
• I isotropic phase. The data between these symbols represent the transition temperatures.
• liquid-crystalline properties of the individual compounds are, unless indicated otherwise, determined in the nematic host mixture ZLI-4792 (commercially available from Merck KGaA, Darmstadt) at a concentration of 10%.
• Root temperature means 20° C., unless indicated otherwise.
• threshold voltage for the present invention relates to the capacitive threshold (V 0 ), also called the Freedericks threshold, unless explicitly indicated otherwise.
• the optical threshold for 10% relative contrast V 10 may also be indicated.
• the test cells used for measurement of the capacitive threshold voltage V 0 and for V 10 are constructed from substrates consisting of soda-lime glass coated with polyimide alignment layers (Durimid 32 with diluent (70% of NMP+30% of xylene) in the ratio 1:4) from Arch Chemicals, which are rubbed antiparallel to one another and have a surface tilt of quasi 0 degrees.
• the area of the transparent, virtually square ITO electrodes is 1 cm 2 .
• the capacitive threshold voltage is determined using a standard commercial high-resolution LCR meter (for example Hewlett Packard 4284A LCR meter).
• the solution is dried using sodium sulfate and evaporated to dryness.
• the crude product is purified by column chromatography (SiO 2 , n-heptane). The further purification is carried out by recrystallisation from ethanol and n-heptane, giving 2-(3,5-difluoro-4′-propylbiphenyl-4-yl)-5-ethylthiophene (PUS-3-2) as a colourless solid (m.p. 45° C.).
• the compound 2-(3,5-difluoro-4′-ethylbiphenyl-4-yl)-5-ethylthiophene (PUS-2-2) is prepared analogously to Example 2 from 4′-ethyl-3,5-difluoro-4-biphenylboronic acid and 2-bromo-5-ethylthiophene.
• the compound 2-(3,5-difluoro-4′-ethylbiphenyl-4-yl)-5-propylthiophene (PUS-2-3) is prepared analogously to Example 2 from 4′-ethyl-3,5-difluoro-4-biphenylboronic acid and 2-bromo-5-propylthiophene.
• the compound 2-(4′-ethyl-2,6-difluorobiphenyl-4-yl)-5-propylthiophene (SUP-3-2) is prepared analogously to Example 1 from 4′-ethyl-2,6-difluoro-4-biphenylboronic acid and 2-bromo-5-propylthiophene.
• ⁇ 1 110 mPa ⁇ s
• the compound 2-(4′-ethyl-2,6-difluorobiphenyl-4-yl)-5-ethylthiophene (SUP-2-2) is prepared analogously to Example 1 from 4′-ethyl-2,6-difluoro-4-biphenylboronic acid and 2-bromo-5-ethylthiophene.
• CRS-3-2 The compound 2-[2,6-difluoro-4-(4-propylcyclohexyl)phenyl]-5-ethylthiophene (“CUS-3-2”) is prepared analogously to Example 3 from 2,5-difluoro-4-(4-propylcyclohexyl)benzeneboronic acid and 2-bromo-5-ethylthiophene.
• the compound 2-(3,5-difluoro-4′-propylbiphenyl-4-yl)-5-vinylthiophene (PUS-3-V) is prepared analogously to Example 3 from 4′-propyl-3,5-difluoro-4-biphenylboronic acid and 2-bromo-5-vinylthiophene.
• a nematic LC mixture according to the invention is formulated as follows:
• a nematic LC mixture according to the invention is formulated as follows:
• a nematic LC mixture according to the invention is formulated as follows:

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